Xerographic apparatus



April 14-, 1964 D. RUBIN XEROGRAPHIC APPARATUS 2 Sheets-Sheet 1 FiledApril 17, 1961 F/Gl INVENTOR- DAN/EL RUB/N BY QAM EQA A A T TOR/V5 YApril 14, 1964 D. RUBIIN XEROGRAPHIC APPARATUS 2 Sheets-Sheet 2 FiledApril 17. 1961 N GP INVENTOR. DAN/EL RUB/N 5% 1. QQ Q A Trams/E UnitedStates Patent 3,128,683 XERGGRAPHEC APPARATUS Daniel Rubin, Rochester,N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation ofNew York Filed Apr. 17, 1961, Ser. No. 103,345 5 Claims. il. 95-1.7)

This invention relates to xerography and in particular to improved.xerographic method and apparatus for reproduction of images onto areusable xerographic plate.

In the process of xerography, for example, as disclosed in CarlsonPatent 2,897,691, issued October 6, 1942, a xerographic plate comprisinga layer of photoconductive insulating material on a conductive backingis given a uniform electric charge over its surface and is then exposedto the subject matter'to be reproduced in the form of activatingradiation, as for example, visible light, usually by conventionalprojection techniques. This exposure discharges the plate areas inaccordance with the radiation intensity that reaches them, and therebycreates an electrostatic latent image on or in the photo conductivelayer. Development of the latent image is effected with anelectrostatically charged, finely divided material such as anelectroscopicpowder or marking particles that are brought into surfacecontact with the photoconductive layer and held thereonelectrostatically in a pattern corresponding to the electrostatic latentimage. Thereafter, the developed xerographic image is utilized forvaried purposes and for example, may be transferred to a support surfaceto which it may be aflixed by any suitable means.

Development of electrostatic latent images is achieved by placing thedeveloping material within a field range of the electrostatic imagewhereby to elfect mutual attraction and, as disclosed in the prior art,includes development by means of a dry powder as disclosed in WalkupPatent 2,618,551, or by means of liquid materials in which developer maybe suspended. A form of liquid development is disclosed in Mayer Patent,U.S. 2,877,133, in which a latent image bearing plate is brought intosurface contact with a liquid of high electrical resistance thatcontains solid developer particles which are attracted therefrom to theselect image portions on the plate. As in dry development, developmentby liquid techniques may be eiiected on an expendable xerographic plateon which the image remains permanently, or in the instance of a reusablexerographic plate, the developed image may be transferred to a secondarysupport surface to which it is permanently affixed and the plate cleanedand cycled for reuse as is now conventional in xerography. Still anotheruse of the formed image may be for scanning or projection purposes suchas disclosed in copending application Ser. No. 738,520, filed May 28,195' 8, in the name of Clark et al.

The present. invention is specifically directed to xerographic methodand apparatus in which development of electrostatic.latentimages on axerographic plate utilizes the principles of liquid development and isdirected in particular for use in connection with reusable xerographicplates from: which a developed image must be removed before recycling ofthe plate.

In either instance of reusing a xerographic plate, the plate must becleaned of developer from previous cycles before recycling. It has beenfound that plates having been developed by techniques of liquiddevelopment are easily cleaned, if cleaning is performed before thedeveloped image has solidified. This may be done by brushing,squeegeeing, or the like, in a developer liquid having a substantialabsence of developer or may even be done after the electrostatic chargeson the. plate are substantially discharged in a developer liquidcontaining developer.

In the instance of cleaning a plate from which a developed image hasbeen transferred to a secondary surface, some developer material isconsumed from the system that must be replenished in a like amount asthat consumed in order to maintain the developer in the liquid at adesired consistency of concentration. In the instance of cleaning aplate where the developed image has not been utilized for forming apermanent image,.it has been discovered that consumption of developercan be reduced and. even substantially eliminated if that which wasutilized for development is restored to the system.

Now in accordance with the invention a xerographic apparatus is providedin which a xerographic plate can have an image developed andsubsequently be cleaned in a liquid development system, which apparatusby the novelty of its combination is rendered completely automatic andadapted for continuous recyling or" a xerographic plate. When theingredients utilized in developing are subsequently'restored to thesystem, substantially no consumption of material occurs and the systemis operative indefinitely at a very minimum of cost.

It is therefore the principal object of the invention to provideimproved xerographic method and apparatus for the reproductionandutilization of processed xerographic images.

his a further object of the invention to improve xerographic method andapparatus for liquid development of electrostatic latent images on axerographic plate.

It is a further object of the invention to provide xerographic methodand apparatus in which electrostatic latent images on a xerographicplate are developed in a liquid development system that has extendedutility withoutsubstantial consumption of materials as compared todevelopment systems of the prior art.

It is a further object of the invention to provide improved xerographicmethod and apparatus for cleaning a xerographic plate after developedimage utilization.

These and other objects are attained in one embodiment of the inventionin which a flexible and endless xerographic plate is advancedcontinuously past a charging station and an exposure station after whichthe plate is immersed in liquid developer to effect image development.The developed image is utilized for protection purposes and the platethereafter is again immersed in the liquid developer while being brushedfor removal'of the previously developed image and restoration of thedeveloper to the liquid.

Embodiments of the invention are disclosed in the accompanying drawingsin which:

FIG; 1 is a schematic side sectional view illustrating a continuousautomatic apparatus employing the method and apparatus of the invention;and,

FIG. 2 is a schematic side sectional view illustrating an alternativecontinuous automatic apparatus employing the method and apparatus of theinvention.

Reference is now had to FIG. l'in which an apparatus utilizingthe methodof the invention isillustrated. The apparatus is housed in a light-tighthousing 10 in which an endless flexible xerographic plate 11 comprisinga photoconductive layer on a flexible conductive backing suchasconductive paper, foil or the like, is continuously advanced oversuitable driven guide rolls. As illustrated, one of the guide rolls isdriven by a motor M- l, which may be stopped momentarily where requiredfor exposing an image to the plate. As the plate advances a uniformelectrostatic charge is-first applied on its surface by a coronagenerating device 12 which may be of a'type disclosed in US. Patent2,836,725 and which is energized from a suitable potential source 13. Onfurther ray tube is projected onto the charged plate surface resultingin an electrostatic latent image that 'is subsequently to be madevisible by development. As the plate continues to advance it moves overa skewed guide roll 16 whereon the plate is directed into a developerliquid 17 of high electrical resistance, and which may be of ahydrocarbon such as kerosene, benzene, etc. as disclosed in theabovecited Mayer patent. The liquid is contained in a reservoir 18wherein development of the electrostatic latent image on the plate iseffected. As the plate emerges from reservoir 18 containing thedeveloped image, it again passes over guide roll .16 without overlappingthe entering plate portion.

Development may be either direct or reversed, i.e., a positive ornegative may be developed in relation to the original exposed image. Asfor. example, where the source of activating radiation is a cathode-raytube or the like having a light image on dark background, it may bepreferred to effect reversal development i.e., to use developerparticles in the liquid that are repelled by the non-image charged areasof the plate to the image uncharged areas thereon resulting in a darkimage on a white background.

The plate bearing the developed image then passes a projection stationdesignated 25, whereat the image is suitably illuminated by lamps 26 and2.7, and the image reflected by a mirror 28 into a lens 2 9, from whichit is projected at increased magnification ratio onto a projectionscreen 30 for viewing by an audience of any convenient size. From theprojection station the plate continues to advance and the developedimage is thereafter removed from the plate as it re-enters the liquid 17while being brushed by brushes 31 driven by motor M-2. After. cleaningthe plate is recycled. A light shield 32 prevents stray light fromreaching the plate surface before development.

Referring to FIG. 2 there is illustrated an alternative embodiment ofapparatus utilizing the method of the invention and contained in alight-tight housing 40. Similarly as in FIG. 1, a flexible and endlessxerographic plate 11 is advanced continuously past a charging stationand an exposure station, after which the plate is immersed in thedeveloper liquid 17 to effect development.

Developer liquid is contained in a reservoir 41. After development theplate passes an exposure station 25 at which the developed image isprojected by suitable optics, as above, onto a screen 30. Followingprojection, the developed image is transferred to a secondary supportsurface 42 at a transfer station generally designated 43. Any transfermeans known in'the art may be employed. In the illustrated embodiment, aweb of secondary support material is drawn from a supply reel 44 overguide roll 45 whereafter the Web contacts the xerographic plate 11 inthe vicinity of a corona generating device 46, 'which may be similar tocorona generator 12 described above and that functions toelectrostatically attract the developed image from the plate onto thesupport material. Thereafter the support material containing thetransferred image advances through a suitable fusing device 47 whichmay, for example, be a heat fuser of the type disclosedin U.S. Patent2,852,651 and wherein the image is permanently affixed to the surface ofthe web. After fusing, the web is drawn through an exit slot 48 onto atakeup reel 49 driven by a motor M-S through a slip-clutch 50 wherebyweb 42 advances at the same lineal rate as the xerographic plate.Alternativelyj the web may be cut into predetermined lengths and stackedin a conventional manner.

After transfer the plate passes to a cleaning station 60 a liquid 61that conveniently may be the same as liquid 17 but without the presenceof developer particles, and is contained in a reservoir 62. Whileimmersed, the plate is brushed by suitable brushes 63 driven by motorM-4. The plate thereafter continues to advance and is recycled. Thereservoir could conveniently be combined in the manner of FIG. 1, butfor practical considerations of design such as degree of physicalseparation two reservoirs in this instance are preferred.

Because developer particles on transfer are being consumed without beingrestored to the developing system in the manner of FIG. 1, an amountwhich is consumed is replenished from a suitable dispensing unit 64containing developer particles 65 that are dispensed in metered amountsto developer liquid 17. The dispenser is operative in response to aregulatory control (not shown) set to effect dispensing substantially inproportion to the rate of consumption. Setting of the regulatory controlmay be automatic or manual. Where required for extended operation,make-up liquid can also be made available to the system. Where it isdesired to maintain liquid 61 substantially free of developer,separation apparatus may be utilized as disclosed in copendingapplication Ser. No. 103,344, filed concurrently herewith, in the nameof Clark et al. Alternatively in the apparatus of FIG. 1, the developedimage could be transferred in a like manner as in FIG. 2. and like-wisein FIG. 2, the transfer operation could be efiected without therequirement of previously projecting the developed image. The advantagesof any such arrangements would be dependent on the purposes for whichthe system. were being employed to efiect visible reproduction.

By the apparatus thus described there is disclosed novel xerographicapparatus for the reproduction of images. The apparatus'is comp-act andefliciently arranged while being particularly adapted for continuousimage formation. While development is effected in the preferredembodiment by immersing the xerographic plate in the liquid it is notintended to be limited thereby since other means may be utilized forbringing the liquid developer into contact with the plate surface, suchas in the Mayer patent cited.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madeWithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specification shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:

1. In a xerographic process including the steps of forming anelectrostatic latent image of copy on a continuously moving xerographicplate, developing the latent image with electroscopic developerparticles from a substantially electrically insulating liquid andutilizing the developed image; the improvement comprising a platecleaning process for removing remaining developer particles from theplate surface after utilization comprising the steps of presenting theplate into contact with an electrically-like liquid as that employed fordeveloping said like liquid having insuflicient developer particleconcentration therein to be capable of developing a latent image andconcomitantly therewith grazing the plate surface whereby the particlesthereon are removed to the like liquid contained therein.

2. In a xerographic process including the steps of forming anelectrostatic latent image of copy on a continuously moving xerographicplate, developing the latent image with electroscopic developerparticles from a substantially electrically insulating liquid, utilizingthe developed image and subjecting the plate to an illuminationintensity capable of uniformly electrically discharging all plate areasthereof; the improvement comprising a plate cleaning process forremoving remaining developer particles from the plate surface afterutilization comprising the steps of presenting the plate into contactwith an electrically-like liquid as that employed for developing, andconcomitantly therewith grazing the plate surface whereby the particlesare removed to the like liquid which at a predetermined developerparticle concentration is usable to effect development of a subsequentlyformed latent image.

3. The improvement according to claim 2 in which grazing is effected bymeans of a rotating brush.

4. The improvement according to claim 2 in which said like liquidcomprises the same developer containing liquid by which development waseffected prior to utilization.

5. The method according to claim 4 in which utilization and illuminationare combined in the step of optical projection of the developed imageand the improvement in- 2,551,582 Carlson May 8, 1951 2,752,833 JacobJuly 3, 1956 2,965,756 Vyverberg Dec. 20, 1960 2,987,660 Walkup June6,1961 3,051,044 McNaney Aug. 28, 1962 3,084,043 Gundlach Apr. 2, 1963UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 128683 April I l 1964 Daniel Rubin i i 1 error appears in the abovenumbered pat- It is hereby certified that I t the said Letters Patentshould read as ent requiring correction and the, corrected below.

Column l line 13 for "2 897 9l" read 2 297 69I column 2 line 46 for"protection" read projection column 4 line 64L before "contained".insert to be Signed and sealed this 10th dayof November 1964.,

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AttestingOfficer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N003, 128 683 April 14 1964 Daniel Rubin or appears the above numbered pat-It is hereby certified. that err ters Patent should read as entrequiring correction and that the said Let corrected below a Column lline 13 for '"2 897 o9l" read 2 297 69l column 2 line 46 for"protection" read projection column l line 64L before "contained" insertto be --0 Signed and sealed this 10th day of November 1964.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER AttestingOfficer

